It is expected that the problem of depletion of valuable metal mineral resources, which has recently become an issue, will be an obstacle to the development of human civilization in the near future.
For example, lithium mineral resources are the raw materials for various IT-related products such as cellular phones, notebook computers, camcorders, etc., which play a significant role in the growth of the Korea economy, as well as for secondary batteries required for hybrid electric vehicles, and are a national strategic metal used in special alloys for aircraft, fuels for thermonuclear power generation, etc.
The reserves of lithium mineral resources in terms of their economics are about 4.1 million tons all over the world and are scarce resources that are expected to be depleted within the next ten years.
Conventional technologies for the recovery of lithium resources from the nature typically include a method for recovering lithium from ore by roasting and sulfuric acid leaching, a method for recovering lithium from a saline lake, a method for recovering lithium from seawater, etc.
The world's lithium resources are mainly concentrated in some countries, and it is practically impossible to extract lithium from the ore and saline lake in Korea where the lithium reserves are minimal However, it is known that even though the concentration lithium in seawater is very low, i.e., 0.17 mg/L, the total amount of lithium dissolved in seawater is tremendous, i.e., about 230 billion tons.
Accordingly, a mineral recovery method, which can selectively extract specific valuable metal ions dissolved in seawater, can reduce the dependency on overseas resources and ensure stable supply of resources. Thus, it can be said that the mineral recovery method is a very important technology that has a high value as an engine for the economic growth of Korea and contributes to the sustainable development of the national economy.
Most of the conventional technologies for the recovery of valuable metals from seawater have been developed based on the ion-exchange and adsorption of inorganic or organic materials for the selective removal of specific metal ions.
Typically, lithium ions are recovered by embedding inorganic compound particles such as manganese oxide into a polymer such as polyvinyl chloride (PVC) or by selectively ion-exchanging lithium ions in a storage comprising a polymer membrane, followed by acid treatment.
The above-described conventional technologies have the advantage of high recovery of lithium ions. However, the time required for the adsorption of specific ions is very long, and thus the economy and efficiency of these technologies are low. Moreover, it is necessary to use toxic materials such as acids in a post-treatment process for the recovery of ions, which causes various problems such as system corrosion, environmental pollution, etc.